1. Field of the Invention
The present invention relates to a hybridization method and hybridization equipment for achieving higher speed and higher efficiency hybridization for biopolymers such as deoxyribonucleic acid (hereafter called DNA), or ribonucleic acid (hereafter called RNA) or proteins attached to DNA, RNA, or the like.
2. Description of the Prior Art
In measuring gene sequences of biopolymers such as DNA, RNA, or proteins attached to RNA or DNA, or the like, DNA chips for hybridization have been used until now.
DNA chips used for hybridization include the one constructed such that multiple electrodes are provided on a substrate and a current source is connected to each electrode, as mentioned, for example, in Michael J. Heller, “An Active Microelectronics Device for Multiplex DNA Analysis,” IEEE Engineering in Medicine and Biology Magazine, 1996, March/April, pp.P100-101. The number of electrodes is about 100 to 10000 and, in general, known different DNAs are fixed to each electrode.
By causing hybridization by passing unknown DNA on a substrate on which such known DNAs are fixed, the unknown DNA is bonded to corresponding DNA sequences. If a fluorescent reagent is bonded to unknown DNA in advance, the sequence of the unknown DNA bonded to known DNA can be known.
The above will be further described in detail below. As shown in FIG. 1(a), a positive voltage is applied to an electrode 81 on which known DNA 82 is fixed. A solution in which unknown DNA 83 can flow is stored (not shown in the drawing) in a region on electrode 81. Unknown DNA 83 is negatively charged and attracted to electrode 81, to which DNA 82 is fixed, moving in the solution as shown in FIG. 1(b). This action increases the concentration of unknown DNA 83 around electrode 81, thus increasing the speed of hybridization.
In addition, if known and unknown DNAs are bonded causing sequence mismatching by mistake, this bonding can be cut off by applying a slight negative voltage to electrode 81 on the contrary after hybridization as shown in FIG. 2(b). As a result, a difference of only one base such as for single nucleotide polymorphisms (SNPs) can be measured with high precision.
However, such conventional method has the following problems:    (1) The method requires individual electrodes to be provided for every site on a DNA chip. This is expensive as well as complicated in construction and it is necessary to ensure wide electrode spaces. Accordingly, this method cannot increase the number of sites and the site pattern on the chip has less degree of freedom.    (2) If a kind of unnecessary DNA having a sequence different from that of the known DNA is once gathered to a site, it is bonded to the known DNA but defectively. For example, as shown in FIG. 3, assume that both unknown DNA (A2) and unknown DNA (B2) are gathered to site A on which known DNA (A1: not shown in the drawing) is fixed. Then, if known DNA (A1) bonded with unknown DNA (A2) causes the appropriate hybridization, unknown DNA (B2) is unnecessary for site A.
On the other hand, assume that both unknown DNA (B2) and unknown DNA (A2) are gathered to site B on which known DNA (B1: not shown in the drawing) is fixed. Then, if known DNA (B1) bonded with unknown DNA (B2) causes the appropriate hybridization, unknown DNA (A2) is unnecessary for site B.